Photographic printing material



June 13, 1939. w. KRIEGER ET AL 2,162,456

- PHOTOGRAPHIC PRINTING MATERIAL Filed Nov. 18, 1957 BY 7K5 @nk THEIR ATTORNEYS PatentedJune 13,1939

PATENT OFFICE 2,182,456 7 PHOTOGRAPHIC PRINTING MATERIAL Wilhelm Krieger and Hans Buchner, Wiesbaden- Biebrich, Germany, assignors to Kalle & Co. Aktiengesells'chai't, Wiesbaden-Biebrich, Germany Application November 18, 1937, Serial No. 175,250 In Germany December 4, 1936 6 Claims.

The present invention relates to photographic printing material.

Photographic prints produced bymeans of the photographic printing materials usually sold 5 commercially, can be generally further copied without difficulty in similar manner to originals. This is in many cases very desirable. In the interest; of secrecy it is, however, often useful if further copying is rendered impossible.

m An object of the present invention is a photographic printing material, which renders possible the production of prints which cannot be copied again by means of the normal photographic printing process. The novel photographic print- !5 ing material differs from the ordinary material, for example, the known diazo type printing paper in that it is coated or impregnated not only with the light sensitive preparation necessary for the production of the. image, but also nonuniformly go with a permanently light absorbing substance, i. e., a light absorbing substance which retains its light absorbing property during an exposure, particularly a light-absorbing substance which is stable to light. The said substance is preferg5 ably applied to the unsensitized rear side of the photographic printing material. It is, however,

also possible to prepare the front side of the paper, for example by applying first the stable light absorbing substance and then the light senso sitive preparation. Similarly thestable' light absorbing substance may be in the interior of the light sensitive material, for example in the interior of paper. In order to obtain a non-uniform preparation it is possible to proceed either by preparing the light sensitive material with said substance only at individual places or by applying at diflerent places diflerent quantities of the substance. It is necessary that the substance is so chosen that it absorbs light rays of those particular wave lengths which are in general employed "in copying, i. e., light of short wave length. The present invention contemplates the use of substantially colorless light-absorbing substances. These also-should possess 45 substantive properties as far as possible, i. e.,

they should. become taken up on the support of the photographic printing material (see Kolloidbeihefte, vol. 34 (1932), p. 218). The employment oi colourless materials has the advantage .0 that the preparation does not present an external appearance. It is, or course, understood that the development of the material according to the invention after exposure has to be performed in such a manner that the substance absorbing ultra-violet light remains on the material.

The following example illustrates the invention: r

A photographic printing paper is printed on the rear side non-uniformly with a 6% solution of the sodium salt of methylumbeliiierone carboxylic acid and is thereupon dried. The accompanying drawing, is a diagrammatic illustration of a printing paper thus prepared wherein reference numeral I designates the base, 2 the uniform light-sensitive layer and 3 the non-uniformly applied substantially colorless ultra-violet light absorbing substance. This printing eflect is not noticeable and prevents further copying of the prints produced with the material.

We claim:

1. Photographic printing material comprising a base, a uniform light-sensitive layer and a substantially colourless substance permanently capable of absorbing ultra-violet lightapplied non: uniformly to said material. 1

2. Photographic printing material comprising a base, a uniform layer comprising a light-sensitive diazo compound and a substantially colorless substance permanently capable of absorbing ultra-violet light applied non-uniformly to said material.

. 3. Photographic printing material comprising a base, a uniform layer comprising a light-sensitive diazo compound and a substantially colorless substance substantive to said base and permanently capable of absorbing ultra-violet light applied non-uniformly to said material.

4. Photographic printing material comprising a base, a uniform layer comprising a light-sensitiye diazo compound applied to one side of said base anda substantially colorless substance permanently capable of absorbing ultra-violet light I printed non-uniformly on the other side of said base. 4

5. Photographic printing material such as is described in claim 4 wherein the substance capable oi. absorbing ultra -violet'light is substantiallystable'to light. j

- 6. Photographic printing paper comprising a base, a uniform light-sensitive layer and a substance comprising the sodium salt of methylumbelliierone carboxylic acid applied non-uniformly to said material. WIIHELM xamaria. HANS BUCENER. 

